Synthesis of 2D/2D structural Ti3C2 MXene/g-C3N4 via the Schottky junction with metal oxides: Photocatalytic CO2 reduction with a cationic scavenger

A series of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites were successfully fabricated by the integration of 2D Ti3C2 MXene and 2D polymeric carbon nitride (CN) with ZnO and Cu2O. The HF etching on Ti3C2 MXene offered significant improvement for the photocatalyst fabrication, while the close 2D/2D junction of Ti3C2/CN created the Schottky junction to enable proficient electron transfer in the ternary nanocomposite. Next, the junction of 2D MXene and 2D CN with the metal oxides (Cu2O and ZnO) prevented the quick recombination of photoexcited electrons and holes and contributed multiple electron pathways for the CO2/CH3OH process. At the same time, the formation of analogue Z-scheme heterojunctions through the synergistic effect of 2D Ti3C2 MXene and 2D metal-free CN with ZnO contributed to the rapid separation and transfer of photogenerated charge carriers. As a result, the photocatalytic CO2 reduction activity of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites was significantly enhanced. Meanwhile, adding a Na2SO3 sacrificial electron donor with pure water and NaHCO3 solvent system supply in CO2 photoreduction experiments contributed to the formation of CH3OH. In particular, the yield of CH3OH was up to 18.72% and 19.98%, 5times and 6-times fold than the pure Cu2O and ZnO, while 3-times fold than the TCCN in a water system. In a NaHCO3 solvent with the sacrificial electron donor, the CH3OH rates over Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O were 22.41% and 20.12%. Taking into account the chemical and structural tunability of ternary nanocomposites, the excellent photocatalytic ability of Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O could be used in the future production of hydrocarbon fuels, as well as increasing the possibility of using 2D MXene in photocatalyst fabrication.